At it's core, Buddhism is about learning non-reaction to both pleasure and pain, treating both as mere sensation. I suppose this practice could be defended in that vein. However, it reminds me more of the Buddha's early ascetic practices, that he himself renounced, declaring that there is no point in actively harming oneself, and that one should instead work to reduce craving and aversion (the two fundamental types of reaction).
There was another article about a small sect of Japanese Buddhist monks that had some horrible practices, like screaming at each other in the morning, and so on. Even stranger (and more horrible) practices exist. But I would not call them Buddhist.
Shingon is a Vajrayana-style mystic tradition of Buddhism: more similar to Tibetan Buddhism than more popular East Asian forms. Also, it has been basically isolated in Japan since about the year 800. Although there is a Chinese school, contact was apparently limited.
The screaming might be part of Zen training. They scream at disciples to focus their mind on whatever they are doing right now. No daydreaming or you get screamed at.
There was another article about a small sect of Japanese Buddhist monks that had some horrible practices, like screaming at each other in the morning, and so on. Even stranger (and more horrible) practices exist. But I would not call them Buddhist.